A wafer storing container is generally provided with a container body for storing a plurality of semiconductor wafers in a state of being arranged in a parallel manner. A wafer load/unload opening for loading or unloading the semiconductor wafers is formed in a front face of the container body of such a wafer storing container. A cover for closing the wafer load/unload opening is provided so as to be removably attached from a front of the wafer load/unload opening.
In order to retain the semiconductor wafers in an unshaken state inside the container body, a back-side retainer is arranged at the back inside the container body as viewed from the wafer load/unload opening, and a cover-side retainer is provided to an inner wall of the cover. The cover-side retainer and the back-side retainer elastically retain outer margins in the vicinities of front-side and back-side ends of the semiconductor wafers.
However, the cover-side retainer does not retain the semiconductor wafers, unless the cover is attached to the wafer load/unload opening of the container body. The back-side retainer can retain only the back side of the semiconductor wafers inside the container body.
Accordingly, wafer support shelves for secondarily mounting the side edges of the semiconductor wafers inside the container body are provided on the right and left sides inside the container body as viewed from the wafer load/unload opening, so as to horizontally support each of the semiconductor wafers until the cover is attached to the container body. When retained by the back-side retainer and the cover-side retainer, the semiconductor wafers are uplifted and separated from the wafer support shelves (for example, Patent Document 1).
When supported by the wafer support shelves, the semiconductor wafers should not be mounted on the entire surface of the wafer support shelves. This is because, when the outer margins of the semiconductor wafers are mounted on the entire range of the arcuate wafer support shelves, particles (scraped particles) are likely to be generated due to friction between the semiconductor wafers and microscopic irregularity on the wafer support shelves, and posture of each of the semiconductor wafers may vary due to profile irregularity (flatness) of the shelves.
Accordingly, it has been proposed that semiconductor wafers are made in point contact or line contact with wafer support shelves (for example, Patent Document 2); or it has been proposed that a semiconductor wafer is horizontally supported at four points in total of wafer support shelves on the right and left sides, by providing four wafer support projections to the wafer support shelves (at one point each on the back and front sides in each of the right and left sides, on the basis of the central position of the semiconductor wafer as viewed from the wafer load/unload opening), the wafer support projections partially mounting an outer margin of the semiconductor wafer (for example, Patent Document 3).